The following book by Choong Mun-keat may be useful for your personal spiritual and academic interest in seeking out ‘the original teachings of the Buddha’, leading to happiness, peace, and understanding:
The Fundamental Teachings of Early Buddhism: A Comparative Study Based on the Sutra-anga portion of the Pali Samyutta-Nikaya and the Chinese Samyukta-agama (Series: Beitrage zur Indologie Band 32; Harrassowitz Verlag, Wiesbaden, 2000).
SuttaCentral